Light projector



P. s. OSGOOD LIGHT PROJECTOR Filed May 25,1921

2 Sheets-Sheet 2 Patented June 16, 1925.

UNITED STATES PATENT OFFICE.

PHILIP S. OSGOOD, 0F CLEVELAND, OHIO.-

LIGHT PROJECTOR.

Application filed May 25, 1321. Serial No. 472,433.

to which it appertains to make and use the same. i

The invention relates to lamps suchas are employed in the use ofvehicles at night, the purpose being to project a beam of hght upona-confined area at a distance.

It consists of a combination of certain 111621.118 employed heretofore,with certain new and essential features, to provide a lamp of newachievement, that is for the conversion of all the light possible from agiven source into a beam. of controlled dimension and shape, with aminimum amount I of diffusion and loss of rays.

In principle and in application this invention is an improvement overexisting lamps of similar purpose in the following respects:

First: It accomplishes its'purpose without causing reflected rays topass from a parabolic surface through a lens, which is fundamentallywasteful on account of the loss in cross rays.

Second: There are no free rays, all of the rays are directed into thecontrolled beam.

Third: It eliminates the use of plane-or tubular surfaces placed in thepath of the beam to prevent lateral escape of light, which surfaces canfunction only at the expense of rays absorbed and also prevent theexpansion of the beam. This feature is of vital importance.

Fourth The control of the shape of the beam and therefore of the fieldof illumination by the use of a lens which is ground to function asdesired. This feature is also of great importance. The lens is made toproject as much as possible of-the total light produced. The remainingrays are projected by a parabolic reflector, not through the lens,'butinto the'beam projected by the lens.

Fifth: The use of a reflector of semispherical shape to focus backthrough the source as much of the light as the lens can encompass.Throwing these light Waves back to the source has the effect ofincreasing the temperature and therefore the efficiency of the filamentin the case that the usual electric lamp is employed. The fact that theyare reflected in an'inverted image also increases the dimension of thesource, and all waves radiate virtually from this one point. Increasingthe temperature of the filament is also desirable particularly becausethe energy of a storage battery such as vehicles make use of isprogressively lowered with age.

Sixth: That given a source of equal light energy 1t will produce a moreintense field of lllumination, size for size, than any other type oflamp, for the simple reason that it brings into that field everyavailable ray. And that all the foregoing objects are accomplished, bythe inexpensive and rugged assembly of easily fabricated parts. I

The invention is hereinafter more fully described, illustrated in'theaccompanying drawings, and specifically pointed out in the claim.

In the accompanying drawings, Fig. 1

is a longitudinal horizontal section of the lamp; Fig. 2, is a frontelevation thereof; Fig. 3 is a diagram illustrating the return of thereflected rays to the source of light; Fig. 4;, is a diagramillustrating the inversion-of the reflected image at the source; Fig. 5,illustrates the effect of the improved lamp, which projects a beam whichis elongated transversely in cross section, and forms a field ofillumination which is nearly circular in form and covers two wheeltracks or a field as large as would be covered by the use of two spotlights. Fig. 6 is an elevation of the vertical edge of the preferableform of lens employed, and Fig. 7 is a plan of the edge of the lenslooking from above thelsame.

' The foregoing advantages are attained by the use'of a reflector ofpart spherical and part parabolic surface, and by an astigniaticlens'which is derived from a plano-convex lens by altering the planesurface of the lens to a horizontal cylindrical preferably concavesurface, thus giving the lens at once different converging powers in thevertical and horizontal'directions. t

In the accompanying Fig, 1, the essential parts embodying the abovementioned improvements are exemplified.

' Here the light is produced in the filament 1 of theincandescentelectric lamp 2, of appropriate voltage and currentcharacteristics. A cone of the light falls upon'the astigmatie lens 3,held in place by a suitable support and ring 4, and is projected afterbeing made less divergent by the lens, its sides being almost parallel.The lens, as mentioned above, projects an elliptical beam whichilluminates a nearly circular field in contrast to the usual elongatedellipticalfield. .Elhe value of this-elliptical beam is obvious in thedrawing of the roadway illumination, as shown in Fig. 5, and will behereinafter discussed further.

Tn the rear, and opposite the cone of light just described, almost awhole hemisphere oflight falls upon the substantially semisphericalportion, 5 of the reflector, which is as nearly concentric with thesource of light as possible, and is designed to reflect the light backagain to the source, that is,

to the filament, and the light continues past the filament to unite withthe cone, falling directly upon, the lens, or, when it passes outside ofthe lens, it falls upon the paralight, from the source, 1, fallsdirectly upon -be seen that all the light is refracted or reflected tothe field intended to be illuminated by the lens, except such smallamounts as fall upon the base, 2, of the lamp, 2, or

the relatively small areas of the lens support, 4.

The lamp is held in thecustomary Edison socket, 2, of single or doublecontact, adapted to this construction, which is not different fromordinary practice. The reflector is surrounded and protected by asuitable case, 6, which may also serve to give the external appearanceto the lamp. The plain glass, 7, is employed merely to protect thereflector and lens from dust, moisture, tarnish, etc., and is held inposition by a'ny suitable arrangement, as shown at 8. The silvered andpolished reflector, 5 and 5", is adapted to give a broad or narrow focusby some simple adjustment, as shown at 9. The reflector is made movablelongitudinally of the exterior casing towards and away from the sourceof light, and is adjusted by means of the spring and set screw, 9, orother simple means, the supports being firmly attached to the shell, (3,passing through the slits, 6, in

the reflector, sufficiently long to permit of appropriate movement ofthe reflector. The

return of the'reflected rays from the semispherical portion of thereflector, 5, to the source is shown in diagrams RR of Fig. 3, and withthe inversion of image, Fig. l.

In Fig. 5 is shown diagramn'latical1y the illuminated field of theelliptical beam. The enormous elongation of the illuminated area alongthe direction of the circular beam is well known in previous use by theshape of the intersection of that beam on a plane surface such as theroad in front of a vehicle,

and the. diagram is self-explanatory. The value of the increased sizeand concentrated scope of the elliptical beam reveals itself in Fig. 5,without argument. The interseetion of the elliptical beam, 3, in Fig. 5,from the improved lamp of this invention, forms a nearly circular fieldof illumination, 46, and covers efficiently both wheel tracks (a) and(6), doing away with the necessity of using two spotlamps to accomplishthe same end.

In further explanation of the action of the lens it might be said thatthe lens in front at Y functions precisely as a convex lens to project aslightly spreading or. diverging beam, with a sufficient amount offlattening caused by a cylindrical concave surfaceiX on the rear face ofthe lens to flatten horizontally the beam so that it will not beelongated in the direction of the roadway or in the direction of theaxis of the beam.

Having described the invention, what I claim as new, and desire tosecure by Let ters Patent, is:

Ina lamp for the purpose set forth, an outer casing, a reflector,provided with a semi-spherical portion and a parabolic portion, a sourceof light and an astigmatic lens spaced therefrom, said source of lightand lens being rigidly secured to said casing within said reflector,said source of light being at the focal point of said semi-sphericalportion of said reflector, said reflector being longitudinallyadjustable in said casing relative to the source of light.

In testimony whereof I hereunto set my hand this 17th day of May, 1921.

PHILIP S. OSGOOD.

In presence of:

S. A. WIL IAMSON, l/VM. M. MONROE.

